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Synopsis

Papular Mucinosis
Papular mucinosis, also known as lichen myxedematosus (LM), includes two subsets of disease with different clinical and pathological findings. The first is a generalized papular and sclerodermoid form, better known as scleromyxedema. The second is a localized papular form.

Scleromyxedema is a rare, chronic, progressive disorder of cutaneous mucin deposition. It affects males and females equally and presents between the ages of 30 and 80. The potential for morbidity and mortality is high. More than 80% of patients have an associated paraproteinemia, typically of the IgG-lambda type, suggesting an underlying plasma cell dyscrasia. The absence of thyroid dysfunctiondifferentiates it from thyroid-related myxedema, which is usually pre-tibial. The etiology of the disorder is unknown.

Diagnosis of scleromyxedema requires mucin deposition, fibroblast proliferation, fibrosis, normal thyroid function tests, and the presence of a monoclonal gammopathy. Bone marrow evaluation in some patients may be normal, or it may range from increased numbers of plasma cells to frank myeloma. Approximately 10% of patients do not have a paraproteinemia.

The criteria for diagnosis of localized LM, on the other hand, include papular or nodular lesions or plaques, mucin deposition with or without fibroblast proliferation, and the absence of both thyroid disease and a monoclonal gammopathy.

Scleromyxedema frequently affects multiple extracutaneous organ systems, with gastrointestinal involvement being the most common. Other organ systems that may be involved include cardiovascular, pulmonary, rheumatologic, and central nervous systems. Visceral disease leads to significant morbidity and can be fatal.

Patients present clinically with multiple 1- to 3-mm waxy dome-shaped or flat-topped papules. These papules may be arranged in a linear pattern, or may coalesce into plaques. The dorsal hands, face, elbows, and extensor extremities are the most commonly involved sites. Diffuse infiltration may occur, presenting with confluent lichenoid plaques, leading to a woody, sclerodermoid quality to the skin. Coalescence of infiltrative lesions on the glabella and forehead may lead to leonine facies. Patients may experience a reduced range of motion of the hands, other extremities, and even the mouth as a result of the disorder. Pruritus may or may not be present.